1. Field of the Invention
The present invention relates to objective lens driving devices and optical information recording/regenerating devices, and particularly to an objective lens driving device and an optical information recording/regenerating device for recording or regenerating information to a plurality of optical information recording media of different kinds with different substrate thicknesses, different recording sensitivities, etc. in a single optical information recording/regenerating device.
2. Description of the Background Art
Optical information recording/regenerating devices have widely spread which optically record and regenerate information using a laser beam such as a semiconductor laser beam, as a light source. In an optical information recording medium used in such a device, e.g., in a read-only compact disc, information is carved in the form of spiral unevenness at intervals of about 1.6 .mu.m on a 1.2 mm thick polycarbonate substrate. The laser beam is applied onto the information surface through the 1.2 mm thick polycarbonate substrate to detect information as a change in intensity of reflected light.
Generally, it is common that the laser beam is applied through a transparent substrate by the optical information recording/regenerating devices as described above, but optical information recording/regenerating media having substrate thicknesses and information track pitches different from those of the compact disc are appearing in order to achieve recording densities higher than that of the compact disc. However, to regenerate such optical information recording media with different substrate thicknesses and track pitches with a conventional optical information recording/regenerating device has been extremely difficult or impossible.
This is due to the following facts: First, since the objective lens for condensing and applying the light beam onto the optical information recording medium is designed so that the aberration becomes the smallest for the thickness of the used substrate, large aberrations occur for a substrate with a different thickness and a light spot which is condensed enough to regenerate information is not formed. Second, the difference in track pitch means a difference in recording density of the optical information recording medium, so that recording and regeneration of information are difficult without using an objective lens dedicated for that recording density.
One method for solving this problem is to switch objective lenses to adapt to different optical information recording media. A conventional optical information recording/regenerating device, however, has an objective lens driving device which is finely movable for focus adjustment and tracking adjustment, but the objective lens driving device does not have a function of switching objective lenses adapted to the respective different optical information recording media.